Effect of poppy (Papaver somniferum L.) fertilization with potassium and magnesium on the seed yield and its quality

In a vegetation pot experiment we explored the effect of fertilizers with potassium (KCl; 0.9 g K2O/6 kg of soil) and magnesium (ESTA Kieserite; 0.3 g MgO/6 kg of soil) applied together or separately to poppy on soil with good K and Mg supply on the seed yield, oil content and cadmium in the seed. Seed yields increased significantly after the application of KCl and ESTA Kieserite, respectively by 23.89% and 21.68%, as compared to the unfertilized control. Combined application of both fertilizers stimulated the yields significantly, i.e. by 15.26%. The seed oil content showed no significant changes among the treatments and ranged only between 42.1 and 43.6%. The pot production of oil in the fertilized treatments increased to 2.21-2.44 g/pot compared to 1.92 g/pot in the unfertilized control. The Cd content in seeds was very low, there were no differences among the treatments and it ranged only between 0.204 and 0.214 mg/kg fresh matter - FM (threshold level of 1.20 mg/kg wet weight). Therefore, the application of both KCl and ESTA Kieserite fertilizers can be recommended on soils well supplied with both nutrients.